The present invention relates to a device which is useful in building tires. Particularly, the present invention relates to an improved roller which is novel and which finds particular utility in stitching two elements of a tire together to form a layered structure.
The principle elements in the art of tire building are well known to include a stitching operation wherein an inner element, or carcass, is brought into intimate contact with an outer element, or tread. A cement is applied between the carcass and tread to adhere one to the other. Of utmost importance to this stitching operation is the application of pressure to insure an adequate bond between the carcass and tread and to eliminate any air that is entrapped between the tread and carcass. Air is usually excluded from the space by the use of pressure rollers as well known in the art. There are three main categories of pressure rollers taught in the art. These can be categorized as spiral rollers, sequential rollers and contouring rollers.
Spiral rollers typically comprise a multiplicity of wheels, or similar device, which travel around the tire in a spiral fashion beginning in the center of the tread and transiting towards the edges. Typically, a pair of wheels work in symmetrical tandem excluding air as both transit linearly towards the outer edge of the tire while the tire rotates on its axis. Exemplary examples include U.S. Pat. Nos. 5,312,502; 5,181,982; 4,341,584; 4,306,931; 4,276,105; 4,057,455; 3,850,719 and 3,850,728. Spiral roller mechanisms tend to compress and spread the tread which causes tread material to accumulate towards the edge of the tire. This is undesirable.
Sequential rollers typically comprise a multiplicity of wheels situated in pairs which are symmetrical about the center of the tread. The roller(s) closest to the center of the tread come into contact with the tread first to exclude air from between the center portion of the tread and carcass. After a suitable time a second set of rollers, displaced towards the edge, are brought into contact with the tread of the tire. Additional sets of rollers, each displaced outwardly relative to the previously contacting rollers, are brought into contact sequentially. Exemplary examples include U.S. Pat. Nos. 4,039,366; 4,004,961 and 3,819,449. The sequential rollers eliminate the problem of outward displacement of tread material but are lacking in their ability to easily conform to differing surface contours. If a change in tire style, or size is required the wheels are replace which is undesirable.
Contouring rollers, the class containing the present invention, typically comprise a multiplicity of independently moving disk around a central core. U.S. Pat. No. 4,052,246 and U.S. Pat. No. 5,330,609 are exemplary references teaching contouring rollers.
Both U.S. Pat. No. 4,052,246 and U.S. Pat. No. 5,330,609 comprise a multiplicity of parallel disk circumferentially surrounding an inflatable tube. The tube is inflated which, in turn, causes the disk to exert pressure on the surface of the tread. The amount of deflection available is limited to the size of the inflatable tube. The range of contour changes with which the existing contouring roller design can be operated is limited thereby diminishing their operating range.